Tracked vehicles such as military tanks and bulldozers have been steered in a conventional manner by a clutch and brake assembly associated with each track of the vehicle. A turning maneuver was performed conventionally by the driver by disengaging the clutch to the track located on the side toward the inside of the turn, and engaging the clutch on the track located towards the outside of the turn. The greater rotational velocity of the outside track as compared to the inside track caused the vehicle to make a curving turn. Sharper turns were accomplished by braking the inside track so that there was very little or no rotation of this track relative to the outside track.
Other conventional apparatus for turning a tracked vehicle have been disclosed. In U.S. Pat. No. 1,253,319 by White, which was reissued as U.S. Pat. No. Re. 14,938, there is disclosed a differential gear for a tracked vehicle which is caused to turn in a right or left direction by application of a braking pressure which causes the braked side of the differential and its corresponding axle to slow down and the unbraked side of the differential and its corresponding axle to speed up.
A power transmission and steering control mechanism for a tracked vehicle is disclosed in U.S. Pat. No. 2,336,912 by Zimmerman, which includes separate differentials for each track which are selectively driven by a third differential.
In Orshansky, U.S. Pat. No. 2,393,557, a differential steering gear for a tracked vehicle was disclosed wherein steering was effected by changing the relative velocity of the tracks by means of a variable volume output hydraulic unit.
Neklutin disclosed a steering mechanism for a tracked vehicle in U.S. Pat. No. 2,763,164, which included a variable speed motor which acted through a differential gear to cause differing rotational velocities of opposing drive shafts to cause a vehicle to turn in a desired direction.
U.S. Pat. No. 3,351,149 by Lundin et al, disclosed a steering mechanism for a tracked vehicle in which opposing right and left shafts for driving the tracks were engaged to a hydraulically driven steering shaft which generated additive and subtractive forces to the drive shafts to cause the vehicle to turn.
Binger et al, disclosed a steering gear for a tracked vehicle in U.S. Pat. No. 3,439,559, wherein the vehicle was turned by a control mechanism which drove the opposing tracks at differential speeds.
In U.S. Pat. No. 3,461,744 by Booth, a steering system for a tracked vehicle was disclosed which utilized a hydraulic system including separate motors/pumps for each track, the outputs being separately adjusted to cause the velocity of one of the tracks to increase and the velocity of the opposing track to decrease thereby turning the vehicle in the selected direction.
A steering differential and braking system for a tracked vehicle was disclosed in U.S. Pat. No. 4,377,094 by Thompson et al, wherein a braking gear on each of two braking axles was used with a differential gear so that a drive input to the differential was divided in a manner that one side of the differential was slowed and the opposing side was speeded up.
In addition to the aforementioned conventional steering apparatus, Ivy in U.S. Pat. No. 2,278,880, disclosed a gearing system for receiving a drive input and for driving an output shaft at selected gear ratios.